Traditional illumination lamps suffer from poor color performance, poor intensity, and/or short usage life. Tungsten filament lamps, for example, while providing high intensity in the illumination pattern, emit a spectral distribution that is yellowish to the human visual system. In addition, tungsten filament lamps generate an enormous amount of heat, normally between 100 to 300 watts of heat energy, which results in raising the temperature of the surrounding environment.
Also, tungsten filament lamps have a low electrical to optical efficiency and, thus, require large amounts of electrical power to generate a high intensity illumination power. The higher amount of electrical power also contributes to the higher amount of heat generated by the tungsten filament lamp. Finally, tungsten lamps have a low life span, usually operating for about 500 hours.
Metal halide arc lamps provide a bluish color and come much closer to replicating white light as defined by the human visual system (e.g., more, for example, than tungsten does). However, metal halide arc lamps cannot be used in many applications because they cannot be hot-striked. That is, they cannot be cycled off and on without a significant restart time. A metal halide arc lamp that is cycled off then back on will not only fail but will also usually be damaged. More recent metal halide arc lamps have a much quicker on-off-on cycle time, however, they have low intensity illumination pattern.
An improved optical system is needed.